As for an ink jet recording-use ink composition, when a water-soluble resin dissolved in the ink composition or a semi-dissolved colloidal dispersion is used as a binder resin, conventionally, the ink composition adheres to the vicinity of a nozzle opening of an ink jet head, which lowers liquid repellency of a nozzle surface, and flight bending, scattering, non-discharge, or the like easily occur, and discharge stability is lowered in some cases. In addition, an ink composition using a water-soluble resin or colloidal dispersion has poor water resistance and solvent resistance. Particularly when the ink composition is printed on a low absorbing substrate or a non-absorbing substrate, a printed matter has insufficient durabilityin some cases.
Meanwhile, a resin emulsion has been conventionally used as a binder resin (refer to Patent Documents 1 and 2). However, Patent Documents 1 and 2 use a resin emulsion having a high acid value of 50 mg KOH/g or more. In this case, an ink composition has poor water resistance and solvent resistance, and a printed matter has insufficient durability in some cases, particularly when the ink composition is printed on a low absorbing substrate or a non-absorbing substrate.
Meanwhile, as for a solvent of an ink jet recording-use ink composition, a low-volatile solvent having a high boiling point has been conventionally used in order to maintain discharge stability. However, in a case where a large amount of a solvent having a high boiling point is used, particularly when the ink composition is printed on a low absorbing substrate or a non-absorbing substrate, a drying property is significantly lowered, a large amount of energy is required for drying, a long time is required for drying, and therefore it is difficult to deal with high-speed continuous printing. Therefore, a printed matter has insufficient durability in some cases.
In addition, aqueous ink compositions generally contain glycerin as a wetting agent (refer to Patent Documents 3 to 5). Drying property becomes a problem in some cases, particularly when the ink composition is printed on a low absorbing substrate or a non-absorbing substrate. In this case, when the amount of glycerin is reduced or glycerin is removed in order to improve the drying property, a nozzle of an ink jet head becomes clogged, or the ink composition is solidified in a flow path of a printer, easily causing a problem in some cases.
There is also prior art concerning an ink composition substantially containing no glycerin (refer to Patent Documents 6 and 7). However, in Patent Document 6, it is necessary to change a printer design for a separate maintenance mechanism. In Patent Document 7, only a special pigment contains no glycerin. Therefore, these techniques are not universally applicable for a general pigment.    Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2008-019431    Patent Document 2: Japanese Unexamined Patent Application, Publication No. 2007-099913    Patent Document 3: Japanese Unexamined Patent Application, Publication No. 2013-199634    Patent Document 4: Japanese Unexamined Patent Application, Publication No. 2010-248477    Patent Document 5: Japanese Unexamined Patent Application, Publication No. 2007-023086    Patent Document 6: Japanese Unexamined Patent Application, Publication No. 2013-256102    Patent Document 7: Japanese Unexamined Patent Application, Publication No. 2011-153250